Comcast said today it will replace its 250-gigabyte data usage cap for residential customers with a 300-GB threshold, and will use market trials to test different approaches to limiting bandwidth.

In a post at the Comcast Voices blog, the company says it will experiment with tiered pricing in some markets. The company will offer two different plans, according to Cathy Avgiris, Comcast’s Executive Vice President and General Manager for Communications and Data Services:

The first new approach will offer multi-tier usage allowances that incrementally increase usage allotments for each tier of high-speed data service from the current threshold. Thus, we’d start with a 300 GB usage allotment for our Internet Essentials, Economy, and Performance Tiers, and then we would have increasing data allotments for each successive tier of high speed data service (e.g., Blast and Extreme). The very few customers who use more data at each tier can buy additional gigabytes in increments/blocks (e.g., $10 for 50 GB).

The second new approach will increase our data usage thresholds for all tiers to 300 GB per month and also offer additional gigabytes in increments/blocks (e.g., $10 per 50 GB).

In both approaches, we’ll be increasing the initial data usage threshold for our customers from today’s 250 GB per month to at least 300 GB per month.

These trials won’t be in all markets. In those areas without trials, Comcast will suspend enforcement of its current data cap. But, Avgiris wrote, the company will still contact you if you’re a data hog. In those cases, Comcast will check to make sure the user’s PC or network doesn’t have malware spewing data onto the Net, or that the customer doesn’t have an unsecured router being abused by a neighbor.

At this point, there’s no indication whether Houston will be one of the trial markets. Avgiris said during a conference call with reporters that the location of the markets have yet to be determined. It also has not been decided when the trials will begin, she said.

Comcast executives emphasized that these changes will affect only a very small percentage of customers. The vast majority of customers come nowhere near its current data cap.

David L. Cohen, Comcast’s Executive Vice President, said the company has not yet determined the additional thresholds in the tiered trial.

In the past, Comcast has warned customers the first time they went over the 250-GB cap. Those who repeatedly went over the cap would have their service suspended for a year. Now, those who use more than 300 GB of data will be billed extra.

Comcast also used the announcement to address accusations that the way it is handling video over its network may be violating the Federal Communications Commission’s new net neutrality rules.

Comcast recently announced a new Xfinity app for showing on-demand movies over Microsoft’s Xbox Live system. The company said movies watched using this app would not count against the data capbecause they traveled over a private network.

In Avgiris’ blog post, she stressed that all video traveling over Internet through Comcast’s connections is treated equally:

Importantly, we have consistently treated all video carried over the public Internet the same whether it comes from our sites or anywhere else on the public Internet. XfinityTV.com, nbc.com, Hulu, Netflix or YouTube, and every other Internet video site (whether our site or a third-party site) is treated, and will continue to be treated, exactly the same. That’s consistent with FCC rules and consistent with what we have always done and continue to do.

But the most important to come out of today’s announcement is that the hard data cap is going away. And, until Comcast decides on which of the two trial models to adopt, the cap is essentially gone. As Cohen put it during the conference call:

The headline today should be: There isn’t a cap anymore. We’re out of the cap business.